We are looking for insights into the mechanisms underlying learning and memory storage. The approach we use is to isolate single-gene mutations that block learning or current memory. Then, using a variety of techniques, we compare our mutations with their parent strains in a search for differences relevant to learning. We have developed a new olfactory discriminative avoidance conditioning procedure that produces a dramatic improvement in learning levels; flies show a 90% probability to make a correct choice. We propose here to use this new conditioning procedure two ways. First, working with ddc mutations (dopa decarboxylase deficient; produces no measurable dopamine or serotonin synthesis and does not learn), we will attempt to revert the learning deficiency by feeding flies monoamine transmitters or their precursors. With this type of procedure we hope to determine which neurotransmitter is principally involved with learning. Second, we propose to screen for and isolate new learning mutations more efficiently. Currently, three of six learning mutants have been characterized biochemically. To pursue our approach further, we need new learning mutants. The strong learning obtained with the new training procedure should enable us to "enrich" the F1 progeny from mutagenized males before screening individual homozygous lines, greatly increasing our efficiency in isolating new mutants.